Generally, semiconductor chips sometimes malfunction due to corrosion of electrodes caused by water content in the atmosphere, and therefore semiconductor chips may be packaged so as to have an airtight structure. Semiconductor chips performing high frequency operation are required to have packages provided with an electromagnetic shielding function to avoid problems such as unstable operation under influences of external radio waves and unnecessary radiation from the semiconductors themselves. Package materials for such chips are generally configured by attaching a metal cap to a base member of CuW or the like, which is however expensive, causing a cost increase. In response to this, in recent years, methods for reducing packaging costs are being actively developed by packaging (CSP structuring) semiconductor chips on chip scales. Structures described in PTLs 1, 2 and 3 are known as typical structures of packaged hollow devices.
PTL 1 describes a case where a HEMT structure which is one of basic transistors of high frequency devices is packaged. According to PTL 1 as shown in FIG. 4 to FIG. 6, a sealing frame is provided on a chip peripheral portion of a device substrate, further a cap is pasted to the sealing frame, and a semiconductor circuit is sealed in a hollow part and packaged. PTL 1 proposes a structure for implementing an electromagnetic shield function by providing the cap and the sealing frame with conductivity. The electromagnetic shield is a function used for a high frequency semiconductor and is intended to suppress influences of radiation of electromagnetic wave generated from the semiconductor circuit on peripheral devices and influences of electromagnetic wave of the peripheral devices on the semiconductor circuit.
According to PTLs 2 and 3, a hollow part is provided between the device substrate and the cap without using any sealing frame but by forming a dent in the cap. According to PTL 2, the electromagnetic shield function is implemented by forming a conductive film in the dent of the cap. According to PTL 3, a heat dissipation electrode is formed on an opposite side of the cap.